The science of the 2019 Mercury transit: How astronomers will study the rare celestial event
By
Nola Taylor Redd
Published Nov 10, 2019 10:26 PM EDT
Grab your telescopes and get some solar filters ready. A rare transit of Mercury across the sun will occur on Nov. 11. This rare astronomical event won't happen again until 2032, so don't miss out!
On Monday (Nov.11), observers and scientists in North America will have their last opportunity to view a rare celestial event for three decades.
Mercury
will cross in front of the sun, as seen from Earth, a process known as a
transit. Although the last transit of Mercury occurred only three years
ago, the next won't happen until 2032 and won't be visible from North
America. These rare events provide the opportunity for scientists to gather both new scientific observations and re-creations of historical ones.
Because it is closer to the sun than Earth, Mercury constantly passes between our planet and our star. But its orbital plane doesn't quite line up with Earth's, so most of the time it appears to dip either above or below the sun when seen from our planet. Only when Mercury's orbit crosses the plane of the Earth as it appears in line with the sun is a transit visible. Such transits are rare; this will be the fourth of 14 to happen this century. (Venus also transits the sun, but even more rarely, occurring in pairs separated by a century from the last set.)
Mercury as seen passing between Earth and the sun during a transit.
(Image: © NASA's Goddard Space Flight Center)
Mercury's transits happen either in May or November, with most
occurring in the fall. These dates change over extremely long timescales
with the evolving orbits of the planets.
"During May transits,
Mercury's closer to us, so it appears larger than in November," David
Rothery, a planetary geoscientist at Open University in the United
Kingdom, previously told Space.com. "You can make more precise measurements in May."
The
tiny planet will transit next in 2032 and 2039, but the sun will be on
the horizon for North American observers, making this year's the last
one visible for the continent until May 2049.
One
of the most common transit observations is to measure when each side of
Mercury comes in contact with the solar limb. These events are usually
referred to as contacts, with the planet being fully in front of the
solar disk during the second and third contact. (The first contact
occurs at the moment when Mercury's silhouette touches the sun's disk
for the first time, marking the beginning of the transit, and the fourth
contact is when Mercury has completely moved off of the sun's disk.)
According to Sky & Telescope, the Citizen Transit of Mercury (ToM) project will attempt to measure the distance between Earth and the sun during Monday's transit. Students will use equipment from a similar project conducted during the 2017 total solar eclipse, called Citizen CATE, to measure when the planet crosses each point of contact.
Click here to continue reading on SPACE.com.
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The science of the 2019 Mercury transit: How astronomers will study the rare celestial event
By Nola Taylor Redd
Published Nov 10, 2019 10:26 PM EDT
Partner Content
Grab your telescopes and get some solar filters ready. A rare transit of Mercury across the sun will occur on Nov. 11. This rare astronomical event won't happen again until 2032, so don't miss out!
On Monday (Nov.11), observers and scientists in North America will have their last opportunity to view a rare celestial event for three decades.
Mercury will cross in front of the sun, as seen from Earth, a process known as a transit. Although the last transit of Mercury occurred only three years ago, the next won't happen until 2032 and won't be visible from North America. These rare events provide the opportunity for scientists to gather both new scientific observations and re-creations of historical ones.
Because it is closer to the sun than Earth, Mercury constantly passes between our planet and our star. But its orbital plane doesn't quite line up with Earth's, so most of the time it appears to dip either above or below the sun when seen from our planet. Only when Mercury's orbit crosses the plane of the Earth as it appears in line with the sun is a transit visible. Such transits are rare; this will be the fourth of 14 to happen this century. (Venus also transits the sun, but even more rarely, occurring in pairs separated by a century from the last set.)
Mercury as seen passing between Earth and the sun during a transit.
(Image: © NASA's Goddard Space Flight Center)
Mercury's transits happen either in May or November, with most occurring in the fall. These dates change over extremely long timescales with the evolving orbits of the planets.
"During May transits, Mercury's closer to us, so it appears larger than in November," David Rothery, a planetary geoscientist at Open University in the United Kingdom, previously told Space.com. "You can make more precise measurements in May."
The tiny planet will transit next in 2032 and 2039, but the sun will be on the horizon for North American observers, making this year's the last one visible for the continent until May 2049.
A historical observation
One of the most common transit observations is to measure when each side of Mercury comes in contact with the solar limb. These events are usually referred to as contacts, with the planet being fully in front of the solar disk during the second and third contact. (The first contact occurs at the moment when Mercury's silhouette touches the sun's disk for the first time, marking the beginning of the transit, and the fourth contact is when Mercury has completely moved off of the sun's disk.)
According to Sky & Telescope, the Citizen Transit of Mercury (ToM) project will attempt to measure the distance between Earth and the sun during Monday's transit. Students will use equipment from a similar project conducted during the 2017 total solar eclipse, called Citizen CATE, to measure when the planet crosses each point of contact.
Click here to continue reading on SPACE.com.
Report a Typo